How to keep the Earth alive

Americans have footprints 10 times bigger than those of people in developing countries. These aren't the ones measured by their shoe sizes, but their "ecological footprints" - the acreage of land and shallow sea needed to keep each person in the style they have come to expect. If everybody in the world were to enjoy American standards of living, at current levels of technological efficiency, humankind would need four more Earths to support it. And in 100 years' time, the human population may have grown so much that half-a-dozen extra planets would be needed.

By then, half the species of plants and animals may have vanished from the one Earth we do have at our disposal. Edward O Wilson, Professor of Entomology at Harvard, wants us to feel this loss as it unfolds around us. He is an elegant essayist, and well rehearsed. The Future of Life is a slimmer version of his 1992 book The Diversity of Life, with less about natural history and more about how to keep it going.

It is also more optimistic, despite all the forests maimed and the species never known to science that must have been obliterated in the intervening 10 years. Even the chapters describing the threats and the losses are backlit by the serenity which pervades the book. Part of this mood seems to be personal: Wilson has reached the stage in life where disagreement seems petty. He opens with a letter to Henry Thoreau, his 19th century predecessor as a philosopher-naturalist, and having risen above the barrier of time, he proceeds on the assumption that all other obstacles to understanding between people are surmountable.

Wilson's positive outlook is also based on the sophistication and energy which conservation organisations have applied to their work. The solutions he describes revolve around a strategy concentrated on the areas which are most biologically precious, and most at risk. This emergency response has the attraction of making the planetary crisis look relatively manageable.

Some progress has already been made. Despite the apparently inexorable advances of the logging companies' bulldozers, their profit margins are as thin as the soil in which tropical forests are rooted. Conservation groups have been able to outbid loggers when land concessions come up for sale.

The "hotspots" most at risk, together with the remaining tropical wildernesses, contain about 70 per cent of the planet's animal and plant species. They could be saved at a cost of around $30 billion. That happens to be about how much the US spends on its military every month, and how much its military spending will rise next year. Bill Gates could pick up the tab and still remain in the World's Richest People top 10.

Comparisons like these are not Wilson's style, though. Even when he notes that the Kyoto Protocol on "greenhouse gases" is foundering, he is too polite to mention that the US scuppered it. He trusts in the enlightenment of corporate lead-ers, while saluting the tree-huggers - "I say bless them all" - on the other hand. Like the "honest, loud-shouting picketers", he invests his idealism in nature.

This is surprising for somebody who understands human nature in biological terms. Wilson believes that we are instinctively "biophilic", which is why we are calmed by a room with a landscape view, or a fishtank in the dentist's waiting room. Be that as it may, the love of nature seems a tenuous sentiment compared to the love of cars or hamburgers. And as an orthodox modern evolutionist, he well understands that individuals act for themselves, not for the good of their species - let alone other species. It takes special conditions to overcome selfishness. The $30 billion question is easy, but the real one is why enlightened thinking should be powerful enough to reconcile 10 billion individual interests, and a host of more powerful ones.

Wilson's ethical instincts must surely be right. We have to be optimistic, or catastrophe really will be inevitable. But although The Future of Life is lucid, memorable and visionary, it's more of a pleasure to read than it should be.